Zelie Pollon

Reuters) - A raging wildfire in Los Alamos on Monday briefly entered the property of the nation's preeminent nuclear facility, Los Alamos National Laboratory, a vast complex that houses research laboratories and a plutonium facility.

A mandatory evacuation has been ordered for the town of Los Alamos, which has a population of about 12,000.

Firefighters were able to douse the flames on the one-acre "spot fire" just inside the southwestern boundary of the lab site, about 25 miles outside Santa Fe, authorities said.

Buildings still have not been touched by flames, and authorities said there was little threat to sensitive areas of the 28,000-acre complex.

The laboratory's plutonium facility is on the northeast side of the complex, while the fire seems to be moving south and east, said another lab spokesman, Kevin Roark.

"The facility is very well protected from any kind of wildland fire threat," said Roark. He said the facility survived a May 2000 wildfire that claimed some lab buildings and did more than $1 billion in damage.

Explosive materials on the laboratory's grounds are stored safely in underground bunkers made of concrete and steel, as well as earthen berms, Roark said.

"This fire is going to be with us for a while. It has the potential to double and triple in size," Los Alamos Fire Chief Doug Tucker said Monday afternoon.

Evacuations for nearby White Rock are still voluntary, but residents have been advised that could change, and Los Alamos evacuees have been told not to go there for shelter.

Due to high winds, all aircraft have been grounded, Tucker said.

The laboratory, which ensures the safety and reliability of the U.S. nuclear stockpile, is a national security research facility located in the Jemez mountains of northern New Mexico. It was set up in 1943 as part of the Manhattan project to create the first atomic bomb and still maintains the nation's largest nuclear weapons arsenal.

"The lab has been here for 60 plus years. We intend to be here a lot longer," said lab spokesman Richard Marquez.

Nuclear watchdog groups are keeping a close eye on the fire, said Jay Coughlin, executive director of Nuclear Watch New Mexico.

The speed at which the fire has grown has surprised fire officials.

"There are a lot of people who are just shocked and stunned at this number," said Santa Fe National Forest spokesman Lawrence Lujan, referring to the estimated 44,000-acre fire.

Fire efforts on Monday were mainly focusing on burnout operations to consume fuel ahead of the fire, what Lujan called fighting "fire with fire."

White Rock resident Edie Cummings, who was evacuated during the fire in 2000, said she and her family have already packed the car in preparation to leave later Monday afternoon if needed. Reservations have been made at a Santa Fe hotel, she said.

"We're still here, but we're all packed. We have the dogs and kids ready to go.